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Question Can zinc supplementation reduce the incidence and severity of acute lower respiratory infections in infants and preschool children in India?
6 month randomised, double blind, placebo controlled trial.
Community based clinic in a city in India.
609 children who were 6–35 months of age (mean age 19 mo, 52% boys), had attended a community based clinic for diarrhoea, and had recovered from the initial diarrhoeal episode. Follow up was 99%.
Children were allocated to zinc gluconate, 10 mg (n=298), or placebo (n=311) given daily in 5 ml of liquid supplement containing vitamins A (800 U), B1 (0.6 mg), B2 (0.5 mg), B6 (0.5 mg), D3 (100 U), and E (3 mg) and niacinamide (10 mg). Duration of treatment was 6 months. Children who had diarrhoea received 10 ml of the supplement while they were ill.
Main outcome measures
Number of episodes of and days with acute lower respiratory infection, which was defined as having a cough and (1) raised respiratory rate or (2) temperature ≥101°F (38.3°C) or the presence of lower chest indrawing.
24 and 44 episodes of acute lower respiratory infection occurred in the zinc (0.19 episodes/child/y) and placebo (0.35 episodes/child/y) groups, respectively. Children in the zinc and placebo groups had 155 and 264 days, respectively with acute lower respiratory infections. Compared with placebo, zinc led to a reduction in the incidence of (p=0.018) and number of days with (p<0.001) acute lower respiratory infections. Because a child could have ≥2 episodes related to one another over the 6 month period, a statistical adjustment was made. After this adjustment, similar results were obtained for incidence (p=0.02) but not for the number of days with acute lower respiratory infections (p=0.054) (table⇓).
A daily dietary zinc supplement led to a decrease in the incidence and severity of acute lower respiratory infections in infants and preschool children in India.
The studies by Sazawal et al and Macknin et al provide different conclusions on zinc treatment for children with lower respiratory infection or the common cold. These studies are preceded by at least 10 randomised controlled trials of zinc lozenges for adult patients with colds (5 had positive results and 5 had negative results) and at least 2 reviews of some of the same trials.1, 2
The study by Sazawal et al could be considered a landmark because it showed that a simple measure such as zinc supplementation reduced respiratory morbidity in preschool children in India. Although valid, some would argue about the practicality of giving treatment because preparations were given by field workers. The study sample represents the poorest socioeconomic stratum of urban society, and it is therefore difficult to extrapolate these findings to the general population.
The study by Macknin et al was well executed. However, no beneficial effects of zinc lozenges on the common cold among schoolchildren were found. This study had several limitations including possible unreliable reporting from students and patient selection from suburban school districts. The authors are laudably forthcoming about the potential biases of this study, and they allude to improvements in design for future trials within the field.
With no consensus between these 2 studies and conflicting results in previous studies, the factors that might explain such diverse findings merit consideration. These might include timing of administration (prophylactically compared with at symptom onset), differing formulations and dosages, baseline nutritional status and zinc levels of study participants, and other socioeconomic factors. Zinc appears to have a role in child health in developing countries, as Sazawal et al have shown. Studies such as these open the field to more studies of children in different geographic locations, with more varied socioeconomic and, possibly, dietary risk factors.
The results of both studies are relevant not only to paediatric nurses and public health nurses but also to health visitors, general practice nurses, and specialist community nurses involved in giving parental guidance. Evidence to support recommendations for zinc lozenges for the common cold and acute lower respiratory infection is lacking. Although many alternative treatments for acute respiratory infections exist,3 none has the evidence to warrant recommendation. More work needs to be done on zinc treatment before it can be recommended.
Both studies emphasise the need for practitioners to present information on zinc to parents in an even handed manner. As with any proposed intervention, nurses need to be able to present a critical appraisal of new developments and a balanced picture of the risks and benefits of potential treatments.
Sources of funding: World Health Organisation Diarrheal Disease Control Program; Thrasher Research Fund; Johns Hopkins Family Health and Child Survival Cooperative Agreement; US Agency for International Development; National Institutes of Health.
For correspondence: Dr R E Black, Department of International Health, Johns Hopkins School of Public Health, Room 5039, 615 N Wolfe Street, Baltimore, MD 21205, USA. Fax +1 410 955 7159.